Synthesis and Properties of Magnetic-Luminescent Fe3O4@ZnO/C Nanocomposites

A Fe3O4@ZnO/C nanocomposite with a core-shell structure was synthesized using the co-precipitation method. To prevent the aggregation of the Fe3O4 magnetic particles, polyethylene glycol (PEG) was added. The X-ray diffractometer (XRD) results confirmed the formation of Fe3O4 and ZnO phases, with Fe3O4 having a cubic crystal system and ZnO having a hexagonal crystal system. Carbon in Fe3O4@ZnO/C had no effect on the crystal structure of Fe3O4@ZnO. Images from transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed that the nanocomposite formed a core-shell structure. The Fourier transform infrared (FTIR) spectra verified the presence of bonds among ZnO, Fe3O4, and carbon. The appearance of the stretching vibration of the C≡C bond on the Fe3O4@ZnO/C sample revealed the nanocomposites’ carbon coupling. Photoluminescence (PL) spectroscopy was used to characterize the optical properties of the nanocomposites. Based on the results of the PL, the sample absorption of visible light was in the wavelength range of 400–700 nm. The photoluminescence of Fe3O4@ZnO differed from that of the Fe3O4@ZnO/C, especially in the deep-level emission (DLE) band. There was a phenomenon of broadening and shift of the band at a shorter wavelength, namely, in the blue wavelength region. Magnetic properties were characterized by vibrating-sample magnetometry (VSM). Based on the VSM results, the sample coupled with carbon exhibited a decrease in magnetic saturation. The presence of carbon changed photon energy into thermal energy. So, this material, apart from being a bioimaging material, can also be developed as a photothermal therapy material.